111103313343domain: NAppears in sequencesNumerator of sum of all elements M(i,j,k) = i*j/k, (i,j,k = 1..n). a(n) = Numerator[Sum[Sum[Sum[i*j/k,{i,1,n}],{j,1,n}],{k,1,n}]].at n=21A099865